SPT7830 10-BIT, 2.5 MSPS, SERIAL OUTPUT A/D CONVERTER FEATURES APPLICATIONS • • • • • • • • • • • • 10-Bit, 1 kHz to 2.5 MSPS Analog-to-Digital Converter Monolithic CMOS Serial Output Internal Sample-and-Hold Analog Input Range: 0 to 2 V Nominal; 3.3 V Max Power Dissipation (Excluding Reference Ladder) 45 mW at +5 V 16 mW at +3.0 V • Single Power Supply: +3 V to +5 V Range • High ESD Protection: 3,000 V Minimum Handheld and Desktop Scanners DSP Interface Applications Portable Digital Radios Portable and Handheld Applications Automotive Applications Remote Sensing GENERAL DESCRIPTION The SPT7830 10-bit, 2.5 MSPS, serial analog-to-digital converter delivers excellent high speed conversion performance with low cost and low power. The serial port protocol is compatible with the serial peripheral interface (SPI) or MICROWIRE™ industry standard, high-speed synchronous MPU interfaces. The large input bandwidth and fast transient response time allow for CCD applications operating up to 2.5 MSPS. The device can operate with a power supply range from +3 V to +5 V with very low power dissipation. The small package size makes this part excellent for hand-held applications where board space is at a premium. The SPT7830 is available in an 8-lead SOIC package over the commercial and industrial temperature ranges. Contact the factory for availability of die. BLOCK DIAGRAM Ground VDD Track-and-Hold SAR Analog Input Clock 10-Bit A/D AAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAA Timing And Control Start Convert Serial Output Logic VREF+ VREF- Data Out ABSOLUTE MAXIMUM RATING (Beyond which damage may occur)1 Supply Voltages VDD ...........................................................................+6 V Output Data Out ................................................................ 10 mA Input Voltages Analog Input ................................................ VREF+ .......................................................... VREF– .......................................................... Clock and SC .............................................. Temperature Operating, ambient ............................... –40 to +85 °C junction ......................................... +175 °C Lead, Soldering (10 seconds) ............................ +300 °C Storage .................................................... –65 to +150 °C –0.7 to +6 V –0.7 to +6 V –0.7 to +6 V –0.7 to +6 V Note: 1. Operation at any Absolute Maximum Ratings is not implied. See Electrical Specifications for proper nominal applied conditions in typical applications. ELECTRICAL SPECIFICATIONS TA = +25 °C, VDD = +5.0 V, VIN = 0 to +3 V, fCLK = 35 MHz, fS = 2.5 MSPS, VREF+ = +3.0 V, VREF– = 0.0 V, unless otherwise specified. PARAMETERS TEST CONDITIONS TEST LEVEL MIN TYP MAX UNITS 10 ±0.5 ±1.0 Guaranteed ±1.0 ±1.5 Bits LSB LSB DC ELECTRICAL CHARACTERISTICS DC Performance Resolution Differential Linearity Integral Linearity No Missing Codes VI VI VI Analog Input Input Voltage Range1 Input Resistance Input Capacitance Input Bandwidth (Small Signal) Offset Gain Error IV VI IV IV IV IV VREF– +4% 5 VREF+ –6% 5 30 –2 –2 +2 +2 V MΩ pF MHz % of FSR % of FSR Reference Input Resistance Voltage Range1 VREF–2 VREF+2 VREF+ – VREF– (∆) Reference Settling Time IV 250 280 350 Ω IV IV IV IV –4% VREF– +∆ 1/10 VDD 0 VREF+ –∆ 2/3 VDD V V V ns Timing Characteristics Maximum Conversion Rate Minimum Conversion Rate Maximum External Clock Rate Minimum External Clock Rate Aperture Delay Time Aperture Jitter Time Data Output LSB Hold Time VI IV VI IV IV IV IV 2.5 1 35 14 TMIN to TMAX 90 6 1.0 14 5 5 8 MSPS kSPS MHz kHz ns ps ns 1 Percentages refer to percent of [(VREF+) – (VREF–)] 2 ∆ = Minimum (VREF+ – VREF–) SPT7830 2 12/29/99 ELECTRICAL SPECIFICATIONS TA = +25 °C, VDD = +5.0 V, VIN = 0 to +3 V, fCLK = 35 MHz, fS = 2.5 MSPS, VREF+ = +3.0 V, VREF– = 0.0 V, unless otherwise specified. PARAMETERS TEST CONDITIONS TEST LEVEL Dynamic Performance Effective Number of Bits fIN = 500 kHz fIN = 1 MHz Signal-to-Noise Ratio fIN = 500 kHz fIN = 1 MHz Harmonic Distortion fIN = 500 kHz fIN = 1 MHz Power Supply Requirements +VDD Supply Voltage +VDD Supply Current Power Dissipation3 TYP MAX UNITS IV IV 8.9 8.5 Bits Bits IV IV 56 55 dB dB IV IV 63 58 dB dB IV IV VI IV VI VDD = +3.0 V VDD = +5.0 V VDD = +3.0 V VDD = +5.0 V MIN 3 5.4 9 16 45 5.5 7 10 22 50 V mA mA mW mW 3 Excluding reference ladder. TEST LEVEL CODES All electrical characteristics are subject to the following conditions: All parameters having min/max specifications are guaranteed. The Test Level column indicates the specific device testing actually performed during production and Quality Assurance inspection. Any blank section in the data column indicates that the specification is not tested at the specified condition. TEST LEVEL I TEST PROCEDURE 100% production tested at the specified temperature. 100% production tested at TA=+25 °C, and sample tested at the specified temperatures. II III IV QA sample tested only at the specified temperatures. V Parameter is a typical value for information purposes only. VI 100% production tested at TA = +25 °C. Parameter is guaranteed over specified temperature range. Parameter is guaranteed (but not tested) by design and characterization data. SPT7830 3 12/29/99 GENERAL DESCRIPTION AND OPERATION should be taken to ensure that the LSB is latched into an external latch with the proper amount of set and hold time. The SPT7830 is a 10-bit analog-to-digital converter that uses a successive approximation architecture to perform data conversion. Each conversion cycle is 14 clocks in length. When the Not Start Convert ( SC) line is held low, conversion begins on the next rising edge of the input clock. When the conversion cycle begins, the data output pin is forced low until valid data output begins. DATA OUTPUT CODING The coding of the output is straight binary. (See table I.) Table I - Data Output Coding ANALOG INPUT +FS -1/2 LSB +1/2 FS +1/2 LSB VREF- The first two clock cycles are used to perform internal offset calibrations and tracking of the analog input. The analog input is then sampled using an internal track-and-hold amplifier on the falling edge of the third clock cycle. On clock cycles 4 through 14, a 10-bit successive approximation conversion is performed, and the data is output starting with the MSB. OUTPUT CODE D9 - DO 11 1111 111Ø ØX XXXX XXXX OO OOOO OOOØ OO OOOO OOOO Ø indicates the flickering bit between logic O and 1. X indicates the flickering bit between logic 1 and O. ANALOG INPUT AND REFERENCE SETTLING TRACK AND HOLD TIMING Serial data output begins with output of the MSB. See the Data Output Timing section for details. Each bit of the data conversion is sequentially determined and placed on the data output pin at the clock rate. This process continues until the LSB has been determined and output. At this point, if the SC line is high, the data output pin will be forced into a high impedance state, and the converter will go into an idle state waiting for the SC line to go low. This is referred to as Single Shot Mode. See Modes of Operation for details. Figure 9 shows the timing relationship between the input clock and SC versus the analog input tracking and reference settling. The analog input is tracked from the fourteenth clock cycle of the previous conversion to the third clock cycle of the current conversion. On the falling edge of the third clock cycle, the analog input is held by the internal sample-andhold. After this sample, the analog input may vary without affecting data conversion. If the SC is either held low through the entire 14 clock conversion cycle (free run mode) or is brought low prior to the trailing edge of the fourteenth clock cycle (synchronous mode), the data output pin goes low and stays low until valid data output begins. Because the chip has either remained selected in the free run mode or has been immediately selected again in the synchronous mode, the next conversion cycle begins immediately after the fourteenth clock cycle of the previous conversion. See Modes of Operation for details. The reference ladder inputs (VREF+ and VREF-) may be changed starting on the falling edge of the thirteenth clock cycle of the previous conversion and must be settled by the falling edge of the third clock cycle of the current conversion. VOLTAGE REFERENCE AND ANALOG INPUT The SPT7830 requires the use of a single external voltage reference for driving the high side of the reference ladder. The VREF+ can be a maximum of 2/3 VDD. For example, if VDD = +5 V, then VREF+ max = (2/3) * 5 V = +3.3 V. The lower side of the ladder is typically tied to AGND (0.0 V), but can be run up to a voltage that is 1/10th of VDD below VREF+: TYPICAL INTERFACE CIRCUIT CLOCK INPUT The SPT7830 requires a 50% ±10% duty cycle clock running at 14 times the desired sample rate. The clock may be stopped in between conversion cycles without degradation of operation (single shot type of operation); however, the clock should remain running during a conversion cycle. VREF- max. = VREF+ - (1/10) * VDD. For example, if VDD = +5 V and VREF+ = 3 V, then VREF- max = 3 V - (1/10)* 5 V = 2.5 V. POWER SUPPLY The +Full Scale (+FS) of the analog input is expected to be 6% of [(VREF+) - (VREF-)] below VREF+ and the -Full Scale (-FS) of the analog input is expected to be 4% of [(VREF+) - (VREF-)] above VREF-. (See figure 1.) The SPT7830 requires only a single supply and operates from 3.0 V to 5.0 V. Fairchild recommends that a 0.01 µF chip capacitor be placed as close as possible to the supply pin. Therefore, Analog +FS = VREF+ - 0.06 * [(VREF+) - (VREF-)], and Analog -FS = VREF- +0.04 * [(VREF+) - (VREF-)]. DATA OUTPUT SET UP AND HOLD TIMING As figure 8 shows, all of the data output bits (except the LSB) remain valid for a duration equivalent to one clock period and delayed by 8 ns after the falling edge of clock. Because the data converter enters into a next conversion ready state at the leading edge of clock 14, the LSB bit is valid for a duration equivalent to only the clock pulse width low and delayed by 8 ns after the falling edge of clock. Care For example, if VREF+ = 3 V and VREF- = 0 V, then Analog +FS = 3 V - 0.06 * [3 V- 0 V ] = 2.82 V, and Analog -FS = 0 V + 0.04 * [3 V - 0 V] = 0.12 V. SPT7830 4 12/29/99 Figure 1 - Analog Input Full-Scale Range MODES OF OPERATION The SPT7830 has three modes of operation.The mode of operation is based strictly on how the SC is used. VREF+ +FS SINGLE SHOT MODE Full-Scale Range 6% of [(VREF+) - (VREF-)] When SC goes low, conversion starts on the next rising edge of the clock (defined as the first conversion clock). The MSB of data is valid 8 ns after the falling edge of the fourth conversion clock. (See figure 8, Data Output Timing.) 4% of [(VREF+) - (VREF-)] -FS VREF- The conversion is complete after 14 clock cycles. At the falling edge of the fourteenth clock cycle, if SC is high (not selected), the data output goes to a high impedance state, and no more conversions will take place until the next SC low event. (See the single shot mode timing diagram in figure 4.) The drive requirements for the analog input are minimal when compared to most other converters due to the SPT7830’s extremely low input capacitance of only 5 pF and very high input resistance of greater than 5 MΩ. SYNCHRONIZED MODE If the input buffer amplifier supply voltages are greater than VDD + 0.7 V or less than Ground - 0.7 V, the analog input should be protected through a series resistor and a diode clamping circuit as shown in figure 2. When SC goes low, conversion will start on the next rising edge of the clock (defined as the first conversion clock). The MSB is valid 8 ns after the falling edge of the fourth conversion clock. Figure 2 - Recommended Input Protection Circuit The first conversion is complete after 14 clock cycles. At any time after the falling edge of the fourteenth clock cycle, SC may go low again to initiate the next conversion. When the SC goes low, the conversion starts on the rising edge of the next clock. (See the synchronized mode timing diagram in figure 5.) AVDD +V D1 Buffer ADC 47 Ω The data output will go to a high impedance state until the next conversion is initiated. D2 -V FREE RUN MODE D1 = D2 = Hewlett Packard HP5712 or equivalent When SC goes low, conversion starts on the next rising edge of the clock (defined as the first conversion clock). The MSB data is valid 8 ns after the falling edge of the fourth conversion clock. INPUT PROTECTION All I/O pads are protected with an on-chip protection circuit shown in figure 3. This circuit provides ESD robustness to >3.0 kV and prevents latch-up under severe discharge conditions without degrading analog transition times. As long as SC is held low, the device operates in the free run mode. New conversions start after every fourteenth cycle with valid data available 8 ns after the falling edge of the fourth clock within each new conversion cycle. Figure 3 - On-Chip Protection Circuit VDD 120 Ω The data output remains low between conversion cycles. (See the free run mode timing diagram in figure 6.) Analog 120 Ω Pad SPT7830 5 12/29/99 Figure 4 - Single Shot Mode Timing Diagram tSC Start Convert Latch MSB 1 A Clock 2 A 3 A 4 A 5 A 6 A 7 A 8 A 9 A 10 A 11 A 12 A 13 A 14 A High Z State A9 Serial Data Out A8 A7 A6 A5 A4 A3 A2 A1 MSB Start Conversion A0 LSB Sample Analog Input Figure 5 - Synchronous Mode Timing Diagram tSC tSC Latch MSB Start Convert 1 A Clock 2 A 3 A 4 A Latch MSB 5 A 6 A 7 A 8 A A9 A8 A7 A6 14 A 13 A 15 A 16 A 1 B 2 B 3 B 4 B 5 B High Z State Serial Data Out A1 MSB Start A0 B9 LSB MSB Sample Analog Input A Sample Analog Input B Figure 6 - Free Run Mode Timing Diagram AA AA AA AA AA AA AA AA Latch MSB Start Convert 1 A Clock 2 A 3 A 4 A Serial Data Out 5 A 6 A 7 A A9 A8 A7 MSB Start Sample Analog Input A 8 A 1 3 A A6 A1 1 4 A 1 B 2 B A0 VDD .01 µF VREF+ 0V VIN 5 B 6 B 7 B B9 B8 B7 MSB LSB Sample Analog Input B td=8 ns VREF+ 4 B Figure 8 - Data Output Timing Figure 7 - Typical Interface Circuit REF IN 3 B td=8 ns td=8 ns td=8 ns +VDD .01 µF Analog In +VDD Data Out 0V VREF- Clock SC 1 4 A 1 3 A 5 A +VDD 0V Clock Data Out Ground 4 A +VDD 0V A9 MSB A1 A0 LSB SPT7830 6 12/29/99 Figure 9 - Analog Input Track-and-Hold Timing and Reference Settling-and-Hold Timing Single Shot Mode (SC high, no B cycle) Synchronous Mode* SC Free Run Mode (SC always Ø) Clock 1 A 2 A 3 A 4 A VREF+ 13 A Ref Hold 14 A 1 B 2 B 3 B 4 B Ref Settling Window** AIN Sample Input Sample Input * The rising edge of the SC line can occur any time between the rising edge of clock 1A and the falling edge of clock 14A. ** The reference settling window can be extended in the synchronous mode by adding extra clocks between conversion cycles. The example shown is the minimum number of clocks required (14) per conversion cycle. PACKAGE OUTLINE 8-Lead SOIC A B INCHES MAX SYMBOL MIN A B C D E F G H I J K 0.187 0.228 0.050 typ 0.014 0.005 0.060 0.055 0.149 0° 0.007 0.016 0.194 0.242 0.019 0.010 0.067 0.060 0.156 8° 0.010 0.035 MILLIMETERS MIN MAX 4.80 5.84 1.27 typ 0.35 0.13 1.55 1.40 3.81 0° 0.19 0.41 4.98 6.20 0.49 0.25 1.73 1.55 3.99 8° 0.25 0.89 H G F C D E I J K SPT7830 7 12/29/99 PIN FUNCTIONS PIN ASSIGNMENTS Name Function Analog In Analog Signal Input Start Convert Start Convert. A high-to-low transition on this input begins the conversion cycle and enables serial data output. Clock Clock Clock that drives A/D conversion cycle and the synchronous serial data output Start Convert Data Out Serial Data. Tri-state serial data output for the A/D result driven by the CLOCK input External VREF+ External voltage reference for top of reference ladder External VREF- External voltage reference for bottom of reference ladder VDD Analog and Digital +3 V to +5 V Power Supply Input GND Analog and Digital Ground External VREF+ 1 8 VDD Analog In 2 7 Data Out External VREF- 3 6 Ground 4 5 ORDERING INFORMATION PART NUMBER TEMPERATURE RANGE PACKAGE SPT7830SCS 0 to +70 °C 8L SOIC SPT7830SIS –40 to +85 °C 8L SOIC SPT7830SCU +25 °C *Please see the die specification for guaranteed electrical performance. Die* DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. LIFE SUPPORT POLICY FAIRCHILD'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. www.fairchildsemi.com © Copyright 2002 Fairchild Semiconductor Corporation SPT7830 8 12/29/99